The invention concerns a method of monitoring a condensate drain, and a flow sensor for detecting flow properties in a pipe and/or a fitting carrying a medium, in particular a condensate drain, and a monitoring device for monitoring at least one condensate drain.
Condensate drains are usually employed in installations in the chemical, pharmaceutical and energy-technology industries in order to drain from the installation a condensate which is formed in vapor lines or containers or in shaping processes. In that case drainage of the condensate must be effected at a given moment in time in order to prevent a so-called water hammer and to provide for effective use of energy. Such a water hammer occurs when vapor is introduced into a liquid at a lower temperature or occurs in such a liquid. In addition the condensate drain should prevent vapor from being discharged in the event that no condensate is present.
In such installations, wear phenomena, contamination and/or deposits can occur, for example, by virtue of erosion due to magnetite formation. That can result in leakages or blockages in condensate drains used in the installations. In that respect, it is not possible to see whether the condensate drain is or is not operating from the exterior, that is to say from outside the installation or the pipes and/or the condensate drain. The operability of the condensate drains used is to be checked in a method of monitoring condensate drains. In that respect, it is necessary to clearly establish whether the condensate drain is functioning in fault-free fashion and whether, in the case of faulty functioning, a leak or a blockage occurs. That is necessary as, for example, blocking condensate drains can lead to considerable reductions in the output of the installation, and leaky condensate drains result in vapor losses which in turn represent a considerable economic loss. In addition, a rise in pressure in condensate networks, that is to say in a system with a plurality of condensate drains, is to be expected. Difficulties caused thereby in regard to drainage can then occur at a number of condensate drains in the installation. In addition, there can be a condensate build-up, which can cause water hammers and can also lead to serious damage in the vapor-condensate system. Usually, a proportion of defective condensate drains of an order of magnitude of 15 to 25% is to be expected in installations without regular checking or maintenance. That failure rate can be markedly reduced by regular checks to be performed.
A number of methods of monitoring a condensate drain are already known. The condensate drains can be checked, for example, by means of sight glasses, by level measurement, and by means of sound measurement. A disadvantage with the specified methods is that the operability of the condensate drain can only be estimated.
The methods based on sound measurement rely on detection of the solid-borne sound which is emitted from the surfaces of the housings of the condensate drains. To be able to assess the operating mode of the condensate drain, the detected intensity of the solid-borne sound is shown on a display device or compared to previously recorded reference data.
In that respect, manual checking of each individual condensate drain is usually required, and that involves a great deal of time and effort in larger installations. Under some circumstances, that leads to relatively long checking intervals so that faults in the condensate drain system cannot be immediately detected and removed.
Usually mechanical contact with the condensate drain being investigated is required to detect solid-borne sound. Governed by the structure involved, the measurement results are relatively closely related to the contact pressure force and the contact pressure angle of the measuring sensor, so that any change in one of those parameters can lead to a inaccurate measurement result. In addition, the contact location must be defined as accurately as possible.
By evaluating exclusively the sound intensity in the ultrasound range, it is not possible to accurately establish whether the condensate drain is just draining or has a water hammer by virtue of damage. That case does not afford clear ascertainment of the working condition.